Torque distribution systems in automotive vehicles have been known for many years. Generally, torque distribution devices either control the torque being transferred to an axle as found in an in-line “hang-on” all wheel drive system or may even control the torque being transferred to each individual wheel as found in a twin “hang-on” all wheel drive system. In a typical “hang-on” all wheel system there is a primary driven axle and a secondary driven “hang-on” axle that is connected via a prop shaft or drive shaft and torque transfer coupling to the primary driven axle. The primary driven axle also includes a differential which divides torque to the side shaft of each axle and then to the wheels. The division of torque between the primary and secondary axles is controlled by the torque transfer coupling which is usually integrated in the secondary axle.
A typical prior art “hang-on” all wheel drive system provides a permanent drive primary axle. However, when the primary axle starts to slip i.e. the wheels are on a slick road condition or loose gravel etc., the prior art systems apply torque in an even manner to each wheel of the secondary axle until the appropriate wheel torque is achieved. This provides a traction performance advantage over other “hang-on” torque distribution systems, under slip conditions similar to that of a limited slip differential. The prior art “hang-on” all wheel drive systems typically are either an active torque on demand system which is one that involves a mechanism that works to prevent an action versus the passive torque on demand system which reacts to an action by a wheel. Generally, the active torque on demand systems will preempt wheel slip by transmitting torque to the secondary drive axle based on known inputs such as wheel speeds, throttle position, g-sensors and other sensors located throughout the automotive vehicle.
However, with the increased traction performance of the prior art systems, a substantial number of draw backs are encountered such as complexity of the torque distribution system, the weight of the torque distribution system and the cost to manufacture and design such system. Furthermore, the prior art torque distribution systems, which generally were front wheel drive base systems, had the torque transfer device placed between the drive shaft and the rear axle pinion. Having the torque transfer device located there adds weight to the front of the axle pinion and also requires further shafts and supports as well as additional housings and associated components to complete the torque transfer between the primary driven axle and the secondary driven axle. There have been numerous attempts to overcome the above-identified problems in the area of conventional driveline systems. Most of these systems have tried to develop a method to reduce the mass, packaging requirements and/or joint angles of conventional axles by integrating the inborn side shafts joint and the differential housing. However, no such integration with an axle module having an axle shaft torque management system that includes speed sensing and an electronically controlled clutch pack has been provided to date.
Therefore, there is a need in the art for an axle module that includes an integration of a torque transfer coupling into a smaller package, having reduced weight and packaging requirements. Furthermore, there is a need in the art for a torque distribution system that can electronically be controlled and thus provide tuning for a specific vehicles desired handling and performance requirements.